[GOLF BALL HAVING A POLYURETHANE COVER(Corporate Docket Number PU2163)]

ABSTRACT

A golf ball with a cover composed of a thermosetting polyurethane that has increased resistance to yellowing is disclosed herein. The golf ball of the present invention is able to accomplish this by providing a cover composed of a thermosetting polyurethane material formed from a polyurethane prepolymer and a curative composed of 20 to 40 parts 4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline and 80 to 60 parts diethyl 2,4-toluenediamine. The cover is preferably formed over a core and boundary layer.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a continuation-in-part application ofU.S. patent application Ser. No. 09/682,866, filed on Oct. 25, 2001,which is a continuation-in-part application of U.S. patent applicationSer. No. 09/562,782, filed on May 2, 2000, now U.S. Pat. No. 6,511,388,which is a divisional application of U.S. patent application Ser. No.09/295,635, filed on Apr. 20, 1999, now U.S. Pat. No. 6,117,024.

FEDERAL RESEARCH STATEMENT

[0002] [Not Applicable]

BACKGROUND OF INVENTION

[0003] 1. Field of the Invention

[0004] The present invention relates to a cover for a golf ball. Morespecifically, the present invention relates to a golf ball cover layercomposed of a thermosetting polyurethane.

[0005] 2. Description of the Related Art

[0006] Conventionally golf balls are made by molding a cover around acore. The core may be wound or solid. A wound core typically compriseselastic thread wound about a solid or liquid center. Unlike wound cores,solid cores do not include a wound elastic thread layer. Solid corestypically may comprise a single solid piece center or a solid centercovered by one or more mantle or boundary layers of material.

[0007] The cover may be injection molded, compression molded, or castover the core. Injection molding typically requires a mold having atleast one pair of mold cavities, e.g., a first mold cavity and a secondmold cavity, which mate to form a spherical recess. In addition, a moldmay include more than one mold cavity pair.

[0008] In one exemplary injection molding process each mold cavity mayalso include retractable positioning pins to hold the core in thespherical center of the mold cavity pair. Once the core is positioned inthe first mold cavity, the respective second mold cavity is mated to thefirst to close the mold. A cover material is then injected into theclosed mold. The positioning pins are retracted while the cover materialis flowable to allow the material to fill in any holes caused by thepins. When the material is at least partially cured, the covered core isremoved from the mold.

[0009] As with injection molding, compression molds typically includemultiple pairs of mold cavities, each pair comprising first and secondmold cavities that mate to form a spherical recess. In one exemplarycompression molding process, a cover material is pre-formed intohalf-shells, which are placed into a respective pair of compression moldcavities. The core is placed between the cover material half-shells andthe mold is closed. The core and cover combination is then exposed toheat and pressure, which cause the cover half-shells to combine and forma full cover.

[0010] As with the above-referenced processes, a casting process alsoutilizes pairs of mold cavities. In a casting process, a cover materialis introduced into a first mold cavity of each pair. Then, a core isheld in position (e.g. by an overhanging vacuum or suction apparatus) tocontact the cover material in what will be the spherical center of themold cavity pair. Once the cover material is at least partially cured(e.g., a point where the core will not substantially move), the core isreleased, the cover material is introduced into a second mold cavity ofeach pair, and the mold is closed. The closed mold is then subjected toheat and pressure to cure the cover material thereby forming a cover onthe core. With injection molding, compression molding, and casting, themolding cavities typically include a negative dimple pattern to impart adimple pattern on the cover during the molding process.

[0011] Materials previously used as golf ball covers include balata(natural or synthetic), gutta-percha, ionomeric resins (e.g., DuPont'sSURLYN®), and polyurethanes. Balata is the benchmark cover material withrespect to sound (i.e. the sound made when the ball is hit by a golfclub) and feel (i.e. the sensation imparted to the golfer when hittingthe ball). Natural balata is derived from the Bully Gum tree, whilesynthetic balata is derived from a petroleum compound. Balata isexpensive compared to other cover materials, and golf balls covered withbalata tend to have poor durability (i.e. poor cut and shearresistance). Gutta percha is derived from the Malaysian sapodilla tree.A golf ball covered with gutta percha is considered to have a harshsound and feel as compared to balata covered golf balls.

[0012] Ionomeric resins, as compared to balata, are typically lessexpensive and tend to have good durability. However, golf balls havingionomeric resin covers typically have inferior sound and feel,especially as compared to balata covers.

[0013] A golf ball with a polyurethane cover generally has greaterdurability than a golf ball with a balata cover. The polyurethanecovered golf ball generally has a better sound and feel than a golf ballwith an ionomeric resin cover. Polyurethanes may be thermoset orthermoplastic. Polyurethanes are formed by reacting a prepolymer with apolyfunctional curing agent, such as a polyamine or a polyol. Thepolyurethane prepolymer is the reaction product of, for example, adiisocyanate and a polyol such as a polyether or a polyester. Severalpatents describe the use of polyurethanes in golf balls. However, golfballs with polyurethane covers usually do not have the distance of othergolf balls such as those with covers composed of SURLYN® materials.

[0014] Gallagher, U.S. Pat. No. 3,034,791 discloses a polyurethane golfball cover prepared from the reaction product of poly(tetramethyleneether) glycol and toluene 2,4-diisocyanates (TDI), either pure TDI or anisomeric mixture.

[0015] Isaac, U.S. Pat. No. 3,989,568 (the '568 patent) discloses apolyurethane golf ball cover prepared from prepolymers and curing agentsthat have different rates of reaction so a partial cure can be made. The'568 patent explains that “the minimum number of reactants is three”.Specifically, in '568 patent, two or more polyurethane prepolymers arereacted with at least one curing agent, or at least one polyurethaneprepolymer is reacted with two or more curing agents as long as thecuring agents have different rates of reaction. The '568 patent alsoexplains that “[o]ne of the great advantages of polyurethane covers madein accordance with the instant invention is that they may be made verythin . . . ”, and “[t]here is no limitation on how thick the cover ofthe present invention may be but it is generally preferred . . . thatthe cover is no more than about 0.6 inches in thickness.” The examplesin the '568 patent only disclose golf balls having covers that are about0.025 inches thick.

[0016] Similar to Isaac, PCT International Publication Number WO99/43394 to Dunlop Maxfli Sports Corporation, discloses using two curingagents to control the reaction time for polyurethane formation. The twocuring agents are a dimethylthio 2,4-toluenediamine and diethyl2,4-toluenediamine, which are blended to control the reaction rate of atoluene diisocyanate based polyurethane prepolymer or a4,4′-diphenylmethane diisocyanate based polyurethane prepolymer.

[0017] Dusbiber, U.S. Pat. No. 4,123,061 (the '061 patent) discloses apolyurethane golf ball cover prepared from the reaction product of apolyether, a diisocyanate and a curing agent. The '061 patent disclosesthat the polyether may be polyalkylene ether glycol orpolytetramethylene ether glycol. The '061 patent also discloses that thediisocyanate may be TDI, 4,4′-diphenylmethane diisocyanate (“MDI”), and3,3′-dimethyl-4,4′-biphenylene diisocyanate (“TODI”). Additionally, the'061 patent discloses that the curing agent may be either a polyol(either tri- or tetrafunctional and not di-functional) such astriisopropanol amine (“TIPA”) or trimethoylol propane (“TMP”), or anamine-type having at least two reactive amine groups such as:3,3′dichlorobenzidene; 3,3′dichloro 4,4′diamino diphenyl methane(“MOCA”); N,N,N′,N′tetrakis (2-hydroxy propyl) ethylene diamine; orUniroyal's Curalon L which is an aromatic diamine mixture.

[0018] Hewitt, et al., U.S. Pat. No. 4,248,432 (the '432 patent)discloses a thermoplastic polyesterurethane golf ball cover formed froma reaction product of a polyester glycol (molecular weight of 800-1500)(aliphatic diol and an aliphatic dicarboxylic acid) with apara-phenylene diisocyanate (“PPDI”) or cyclohexane diisocyanate in thesubstantial absence of curing or crosslinking agents. The '432 patentteaches against the use of chain extenders in making polyurethanes. The432 patent states, “when small amounts of butanediol-1,4 are mixed witha polyester . . . the addition results in polyurethanes that do not havethe desired balance of properties to provide good golf ball covers.Similarly, the use of curing or crosslinking agents is not desired . . .”.

[0019] Holloway, U.S. Pat. No. 4,349,657 (the '657 patent) discloses amethod for preparing polyester urethanes with PPDI by reacting apolyester (e.g. prepared from aliphatic glycols having 2-8 carbonsreacted with aliphatic dicarboxylic acids having 4-10 carbons) with amolar excess of PPDI to obtain an isocyanate-terminated polyesterurethane (in liquid form and stable at reaction temperatures), and thenreacting the polyester urethane with additional polyester. The '657patent claims that the benefit of this new process is the fact that acontinuous commercial process is possible without stability problems.The '657 patent further describes a suitable use for the resultantmaterial to be golf ball covers.

[0020] Wu, U.S. Pat. No. 5,334,673 (the '673 patent) discloses apolyurethane prepolymer cured with a slow-reacting curing agent selectedfrom slow-reacting polyamine curing agents and difunctional glycols(i.e., 3,5-dimethylthio-2,4-toluenediamine,3,5-dimethylthio-2,6-toluenediamine, N,N′-dialkyldiamino diphenylmethane, trimethylenegly-col-di-p-aminobenzoate,polytetramethyleneoxide-di-p-aminobenzoate, 1,4-butanediol,2,3-butanediol, 2,3-dimethyl-2,3-butanediol, ethylene glycol, andmixtures of the same). The polyurethane prepolymer in the '673 patent isdisclosed as made from a polyol (e.g., polyether, polyester, orpolylactone) and a diisocyanate such as MDI or TODI. The polyetherpolyols disclosed in the '673 patent are polytetramethylene etherglycol, poly(oxypropylene) glycol, and polybutadiene glycol. Thepolyester polyols disclosed in the '673 patent are polyethylene adipateglycol, polyethylene propylene adipate glycol, and polybutylene adipateglycol. The polylactone polyols disclosed in the '673 patent arediethylene glycol initiated caprolactone, 1,4-butanediol initiatedcaprolactone, trimethylol propane initiated caprolactone, and neopentylglycol initiated caprolactone.

[0021] Cavallaro, et al., U.S. Pat. No. 5,688,191 discloses a golf ballhaving core, mantle layer and cover, wherein the mantle layer is eithera vulcanized thermoplastic elastomer, functionalized styrene-butadieneelastomer, thermoplastic polyurethane, metallocene polymer or blends ofthe same and thermoset materials.

[0022] Wu, et al., U.S. Pat. No. 5,692,974 discloses golf balls havingcovers and cores that incorporate urethane ionomers (i.e. using analkylating agent to introduce ionic interactions in the polyurethane andthereby produce cationic type ionomers).

[0023] Sullivan, et al., U.S. Pat. No. 5,803,831 (the '831 patent)discloses a golf ball having a multi-layer cover wherein the inner coverlayer has a hardness of at least 65 Shore D and the outer cover layerhas a hardness of 55 Shore D or less, and more preferably 48 Shore D orless. The '831 patent explains that this dual layer constructionprovides a golf ball having soft feel and high spin on short shots, andgood distance and average spin on long shots. The '831 patent providesthat the inner cover layer can be made from high or low acid ionomerssuch as SURLYN®, ESCOR® or IOTEK®, or blends of the same, nonionomericthermoplastic material such as metallocene catalyzed polyolefins orpolyamides, polyamide/ionomer blends, polyphenylene ether/ionomerblends, etc., (having a Shore D hardness of at least 60 and a flexmodulus of more than 30000 psi), thermoplastic or thermosettingpolyurethanes, polyester elastomers (e.g. HYTREL®), or polyether blockamides (e.g. PEBAX®), or blends of these materials. The '831 patent alsoprovides that the outer cover layer can be made from soft low modulus(i.e. 1000-10000 psi) material such as low-acid ionomers, ionomericblends, non-ionomeric thermoplastic or thermosetting materials such aspolyolefins, polyurethane (e.g. thermoplastic polyurethanes like TEXIN®,PELETHANE®, and thermoset polyurethanes like those disclosed in Wu, U.S.Pat. No. 5,334,673), polyester elastomer (e.g. HYTREL®), or polyetherblock amide (e.g. PEBAX®), or a blend of these materials.

[0024] Hebert, et al., U.S. Pat. No. 5,885,172 (the '172 patent)discloses a multilayer golf ball giving a “progressive performance”(i.e. different performance characteristics when struck with differentclubs at different head speeds and loft angles) and having an outercover layer formed of a thermoset material with a thickness of less than0.05 inches and an inner cover layer formed of a high flexural modulusmaterial. The '172 patent provides that the outer cover is made frompolyurethane ionomers as described in Wu, et al., U.S. Pat. No.5,692,974, or thermoset polyurethanes such as TDI ormethylenebis-(4-cyclohexyl isocyanate) (HMDI), or a polyol cured with apolyamine (e.g. methylenedianiline (MDA)), or with a tri-functionalglycol (e.g., N,N,N′,N′-tetrakis(2-hydroxpropyl)ethylenediamine). The'172 also provides that the inner cover has a Shore D hardness of 65-80,a flexural modulus of at least about 65,000 psi, and a thickness ofabout 0.020-0.045 inches. Exemplary materials for the inner cover areionomers, polyurethanes, polyetheresters (e.g. HYTREL®), polyetheramides(e.g., PEBAX®), polyesters, dynamically vulcanized elastomers,functionalized styrene-butadiene elastomer, metallocene polymer, blendsof these materials, nylon or acrylonitrile-butadiene-styrene copolymer.

[0025] Wu, U.S. Patent Number 5,484,870 (the '870 patent) discloses golfballs having covers composed of a polyurea composition. The polyureacomposition disclosed in the '870 patent is a reaction product of anorganic isocyanate having at least two functional groups and an organicamine having at least two functional groups. One of the organicisocyanates disclosed by the '870 patent is PPDI.

[0026] Although the prior art has disclosed golf ball covers composed ofmany different polyurethane materials, none of these golf balls haveproven completely satisfactory. One particular dissatisfaction has beenthe yellowing of thermosetting polyurethane covers upon exposure tosunlight (ultraviolet radiation). Thus, there remains a need forthermosetting polyurethane covers that have reduced yellowing whilemaintaining the other desired properties of a thermosetting polyurethanecover.

SUMMARY OF INVENTION

[0027] The present invention provides a golf ball that has a covercomposed of a thermosetting polyurethane that has increased resistanceto yellowing. The golf ball of the present invention is able toaccomplish this by providing a cover composed of a thermosettingpolyurethane material formed from a polyurethane prepolymer and acurative composed of 20 to 40 parts4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline and 80 to 60 partsdiethyl 2,4-toluenediamine.

[0028] One aspect of the present invention is a golf ball including acore and a cover. The cover is composed of a thermosetting polyurethanematerial formed from reactants including a polyurethane prepolymer and4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline. The cover has anaerodynamic surface geometry thereon.

[0029] Another aspect of the present invention is a golf ball includinga core, a boundary layer and a cover. The core is a polybutadienemixture and has a diameter ranging from 1.35 inches to 1.64 inches. Thecore also has a PGA compression ranging from 50 to 90. The boundarylayer is formed over the core and is composed of a blend of ionomermaterials. The boundary layer has a thickness ranging from 0.020 inch to0.075 inch and a Shore D hardness ranging from 50 to 75 as measuredaccording to ASTM-D2240. The cover is formed over the boundary layer.The cover is composed of a thermosetting polyurethane material formedfrom reactants including a polyurethane prepolymer and a curativecomposed of 20 to 40 parts4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline and 80 to 60 partsdiethyl 2,4-toluenediamine. The cover has a Shore D hardness rangingfrom 30 to 60 as measured according to ASTM-D2240. The cover also has athickness ranging from 0.015 inch to 0.040 inch and an aerodynamicsurface geometry thereon.

[0030] Having briefly described the present invention, the above andfurther objects, features and advantages thereof will be recognized bythose skilled in the pertinent art from the following detaileddescription of the invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0031]FIG. 1 illustrates a perspective view of a golf ball of thepresent invention including a cut-away portion showing a core, aboundary layer, and a cover.

[0032]FIG. 2 illustrates a perspective view of a golf ball of thepresent invention including a cut-away portion core and a cover.

DETAILED DESCRIPTION

[0033] As illustrated in FIG. 1, the golf ball of the present inventionis generally indicated as 10. The golf ball 10 includes a core 12, aboundary layer 14 and a cover 16. Alternatively, as shown in FIG. 2, thegolf ball 10 may only include a core 12 and a cover 16. The cover 16 ispreferably composed of a thermosetting polyurethane material formed froma toluene diisocyanate prepolymer and4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline. In a preferredembodiment, the cover 16 is formed over a boundary layer 14 and core 12,as shown in FIG. 1. Alternatively, the cover 16 is formed over the core12, as shown in FIG. 2. Those skilled in the art will recognize that thecore may be solid, hollow, multi-piece or liquid-filled, and theboundary layer may be partitioned into additional layers, withoutdeparting from the scope and spirit of the present invention.

[0034] As mentioned above, the thermosetting polyurethane material isformed from a polyurethane prepolymer and a curative composed of a4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline. The polyurethaneprepolymer is preferably a polypropylene glycol terminated toluenediisocyanate prepolymer, a polytetramethylene ether glycol terminatedtoluene diisocyanate prepolymer, or a polytetramethylene ether glycolterminated hexamethylene diisocyanate prepolymer. In a furtherembodiment, the thermosetting polyurethane material is formed from apolypropylene glycol terminated toluene diisocyanate prepolymer and acurative composed of 4,4′-methylenebis-(3-chloro,2,6-diethyl)-anilineand diethyl 2,4-toluenediamine. A preferred polypropylene glycolterminated toluene diisocyanate prepolymer is available from UniroyalChemical Company of Middlebury, Conn., under the tradename ADIPRENE®LFG960. A preferred polytetramethylene ether glycol terminated toluenediisocyanate prepolymer is available from Uniroyal Chemical Company ofMiddlebury, Conn., under the tradename ADIPRENE®LF930. A preferredpolyester terminated toluene diisocyanate prepolymer is available fromUniroyal Chemical Company of Middlebury, Conn., under the tradenameADIPRENE®LF1900A. Preferred polytetramethylene ether glycol terminatedhexamethylene diisocyanate prepolymers are available from UniroyalChemical under the tradenames ADIPRENE® LFH750, ADIPRENE® LFH749 andADIPRENE® LFH720, which are both aliphatic polyurethane prepolymers.

[0035] Diethyl 2,4-toluenediamine is available from AlbemarleCorporation of Baton Rouge, La. under the tradename ETHACURE® 100.4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline is available from AirProducts and Chemicals Inc., of Allentown, Pa., under the tradenameLONZACURE™.

[0036] The curative mixture for the cover 16 may have numerousvariations. The curative mixture includes4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline in order to control thereaction time and to affect the diminished yellowing of the cover afterexposure to sunlight. In a preferred embodiment, the curative mixture iscomposed of 20 to 40 parts4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline and 80 to 60 partsdiethyl 2,4-toluenediamine. A most preferred curative mixture iscomposed of 30 parts 4,4′-methylenebis-(3-chloro,2,6-diethyl)-anilineand 70 parts diethyl 2,4-toluenediamine.

[0037] The ratio of the polyurethane prepolymer to curative isdetermined by the nitrogen-carbon-oxygen group (“NCO”) content of thepolyurethane prepolymer. For example, the NCO content of thepolypropylene glycol terminated toluene diisocyanate prepolymer ispreferably in the range of 3.0% to 6.0%, more preferably in the range of4.0% to 5.75%, and most preferably 5.70%. The NCO content of thepolytetramethylene ether glycol terminated toluene diisocyanateprepolymer is preferably in the range of 3.75% to 7.0%, more preferablyin the range of 4.0% to 5.75%, and most preferably 5.70%. The NCOcontent of the polytetramethylene ether glycol terminated hexamethylenediisocyanate prepolymer is preferably in the range of 8.0% to 12.0%,more preferably in the range of 10.0% to 11.5%, and most preferably 11%.The weight ratio of the polyurethane prepolymer to the curative ispreferably in the range of about 10:1 to about 30:1.

[0038] Prior to curing, the polyurethane prepolymer and curative arepreferably stored separately. The polyurethane material is formed byfirst heating and mixing the polyurethane prepolymer with the curativein a mold, and then curing the mixture by applying heat and pressure fora predetermined time period. Additionally, a catalyst (e.g. dibutyl tindilaurate, a tertiary amine, etc.) may be added to the mixture toexpedite the casting process. Specific suitable catalysts include TEDAdissolved in di propylene glycol (such as TEDA L33 available from WitcoCorp. Greenwich, Conn., and DABCO 33 LV available from Air Products andChemicals Inc.,) which may be added in amounts of 2-5%, and morepreferably TEDA dissolved in 1,4-butane diol which may be added inamounts of 2-5%. Another suitable catalyst includes a blend of 0.5% 33LVor TEDA L33(above) with 0.1% dibutyl tin dilaurate (available from WitcoCorp. or Air Products and Chemicals, Inc.) which is added to a curativesuch as VIBRACURE®A250. Furthermore, additives such as colorants mayalso be added to the mixture.

[0039] The polyurethane prepolymer is preferably degassed and warmed ina first holding container prior to processing of the cover 16. Theprocessing temperature for the polyurethane prepolymer is preferably inthe range of about 100-220° F., and most preferably in the range ofabout 120-200° F. The polyurethane prepolymer is preferably flowablefrom the first holding container to a mixing chamber in a range of about200-1100 grams of material per minute, or as needed for processing. Inaddition, the polyurethane prepolymer material may be agitated in thefirst holding container, in the range of 0-250 rpm, to maintain a moreeven distribution of material and to eliminate crystallization.

[0040] The curative is preferably degassed and warmed in a secondholding container prior to processing of the cover 16. The processingtemperature for the curative is preferably in the range of about 50-230°F., and most preferably in the range of about 80-200° F. The curative ispreferably flowable from the second holding container to the mixingchamber in the range of about 15-75 grams of material per minute, or asneeded. If a catalyst is used for processing the cover 16, then thecatalyst is added to the curing agent in the second holding container toform a curative mixture. Suitable catalyst are described above. Thecurative and catalyst are agitated, in the range of about 0 to 250 rpm,to maintain an even distribution of catalyst in the curative mixture inthe second holding container. It is preferred that the catalyst is addedin an amount in the range of about 0.25-5% by weight of the combinedpolyurethane prepolymer and curative. Additives may be added to thecurative mixture as desired. It was discovered that hydrolyticinstability of the polyurethane polymer may be avoided by the additionof a stabilizer such as STABOXYL® (available from Rheinchemie, Trenton,N.J.), in amounts of about 0.25-5% of the polyurethane.

[0041] The polyurethane prepolymer and curative mixture are preferablyadded to the common mixing chamber at a temperature in the range ofabout 160-220° F. A colorant material, such as, for example, titaniumdioxide, barium sulfate, and/or zinc oxide in a glycol or castor oilcarrier, and/or other additive material(s) as are well known in the art,may be added to the common mixing chamber. The amount of colorantmaterial added is preferably in the range of about 0-10% by weight ofthe combined polyurethane prepolymer and curative materials, and morepreferably in the range of about 2-8%. Other additives, such as, forexample, polymer fillers, metallic fillers, and/or organic and inorganicfillers (e.g. polymers, balata, ionomers, etc.) may be added as well toincrease the specific gravity of the polyurethane cover 16 of thepresent invention. It was discovered that the addition of barytes(barium sulfate) or a blend of barytes and titanium dioxide (preferablyadded in a carrier glycol and/or castor oil) to the mixture, in theamounts of about 0.01-30%, may add sufficient weight to the polyurethanecover 16. The added weight to the cover 16 allows for a lower specificgravity for the core 12 thereby allowing for an increased resiliency ofthe core 12. The entire mixture is preferably agitated in the mixingchamber in the range of about 1 to 250 rpm prior to molding. A moredetailed explanation of the process is set forth in U.S. Pat. No.6,200,512, entitled Golf Balls And Methods Of Manufacturing The Same,filed on Apr. 20, 1999, assigned to Callaway Golf Company, and which ishereby incorporated by reference in its entirety.

[0042] The core 12 of the golf ball 10 is the “engine” for the golf ball10 such that the inherent properties of the core 12 will stronglydetermine the initial velocity and distance of the golf ball 10. Ahigher initial velocity will usually result in a greater overalldistance for a golf ball. In this regard, the Rules of Golf, approved bythe United States Golf Association (“USGA”) and The Royal and AncientGolf Club of Saint Andrews, limits the initial velocity of a golf ballto 250 feet (76.2m) per second (a two percent maximum tolerance allowsfor an initial velocity of 255 per second) and the overall distance to280 yards (256m) plus a six percent tolerance for a total distance of296.8 yards (the six percent tolerance may be lowered to four percent).A complete description of the Rules of Golf are available on the USGAweb page at www.usga.org. Thus, the initial velocity and overalldistance of a golf ball must not exceed these limits in order to conformto the Rules of Golf. Therefore, the core 12 for a USGA approved golfball is constructed to enable the golf ball 10 to meet, yet not exceed,these limits.

[0043] The coefficient of restitution (“COR”) is a measure of theresilience of a golf ball. The COR is a measure of the ratio of therelative velocity of the golf ball after direct impact with a hardsurface to the relative velocity before impact with the hard surface.The COR may vary from 0 to 1, with 1 equivalent to a completely elasticcollision and 0 equivalent to a completely inelastic collision. A golfball having a COR value closer to 1 will generally correspond to a golfball having a higher initial velocity and a greater overall distance. Ifthe golf ball has a high COR (more elastic), then the initial velocityof the golf ball will be greater than if the golf ball had a low COR. Ingeneral, a higher compression core will result in a higher COR value.

[0044] The core 12 of the golf ball 10 is generally composed of a blendof a base rubber, a cross-linking agent, a free radical initiator, andone or more fillers or processing aids. A preferred base rubber is apolybutadiene having a cis-1,4 content above 90%, and more preferably98% or above.

[0045] The use of cross-linking agents in a golf ball core is wellknown, and metal acrylate salts are examples of such cross-linkingagents. For example, metal salt diacrylates, dimethacrylates, ormono(meth)acrylates are preferred for use in the golf ball cores of thepresent invention, and zinc diacrylate is a particularly preferredcross-linking agent. A commercially available suitable zinc diacrylateis SR-416 available from Sartomer Co., Inc., Exton, Pa. Other metal saltdi- or mono-(meth)acrylates suitable for use in the present inventioninclude those in which the metal is calcium or magnesium. In themanufacturing process it may be beneficial to pre-mix some cross-linkingagent(s), such as, e.g., zinc diacrylate, with the polybutadiene in amaster batch prior to blending with other core components.

[0046] Free radical initiators are used to promote cross-linking of thebase rubber and the cross-linking agent. Suitable free radicalinitiators for use in the golf ball core 12 of the present inventioninclude peroxides such as dicumyl peroxide, bis-(t-butyl peroxy)diisopropyl benzene, t-butyl perbenzoate, di-t-butyl peroxide,2,5-dimethyl-2,5-di-5-butylperoxy-hexane, 1,1-di (t-butylperoxy)3,3,5-trimethyl cyclohexane, and the like, all of which are readilycommercially available.

[0047] Zinc oxide is also preferably included in the core formulation.Zinc oxide may primarily be used as a weight adjusting filler, and isalso believed to participate in the cross-linking of the othercomponents of the core (e.g. as a coagent). Additional processing aidssuch as dispersants and activators may optionally be included. Inparticular, zinc stearate may be added as a processing aid (e.g. as anactivator). Any of a number of specific gravity adjusting fillers may beincluded to obtain a preferred total weight of the core 12. Examples ofsuch fillers include tungsten and barium sulfate. All such processingaids and fillers are readily commercially available. The presentinventors have found a particularly useful tungsten filler is WP102Tungsten (having a 3 micron particle size) available from AtlanticEquipment Engineers (a division of Micron Metals, Inc.), Bergenfield,N.J.

[0048] Table One below provides the ranges of materials included in thepreferred core formulations of the present invention. TABLE ONEComponent Preferred Range Most Preferred Range Polybutadiene    100parts    100 parts Zinc diacrylate   20-35 phr   25-30 phr Zinc oxide   0-50 phr    5-15 phr Zinc stearate    0-15 phr    1-10 phr Peroxide0.2-2.5 phr 0.5-1.5 phr Filler As desired As desired (e.g. tungsten)(e.g. 2-10 phr) (e.g. 2-10 phr)

[0049] In the present invention, the core components are mixed andcompression molded in a conventional manner known to those skilled inthe art. In a preferred form, the finished core 12 has a diameter ofabout 1.35 to about 1.64 inches for a golf ball 10 having an outerdiameter of 1.68 inches. The core weight is preferably maintained in therange of about 32 to about 40 g. The core PGA compression is preferablymaintained in the range of about 50 to 90, and most preferably about 55to 80.

[0050] As used herein, the term “PGA” compression is defined as follows:

[0051] PGA compression value=180—Riehle compression value

[0052] The Riehle compression value is the amount of deformation of agolf ball in inches under a static load of 200 pounds, multiplied by1000. Accordingly, for a deformation of 0.095 inches under a load of 200pounds, the Riehle compression value is 95 and the PGA compression valueis 85.

[0053] As is described above, the present invention preferably includesat least one boundary layer 14 that preferably is composed of athermoplastic (e.g. thermoplastic or thermoplastic elastomer) or a blendof thermoplastics (e.g. metal containing, non-metal containing or both).However, the golf ball 10 may have several boundary layers 14 disposedbetween the core 12 and the cover 16. Most preferably the boundary layer14 is composed of at least one thermoplastic that contains organic chainmolecules and metal ions. The metal ion may be, for example, sodium,zinc, magnesium, lithium, potassium, cesium, or any polar metal ion thatserves as a reversible cross-linking site and results in high levels ofresilience and impact resistance. Suitable commercially availablethermoplastics are ionomers based on ethylene copolymers and containingcarboxylic acid groups with metal ions such as described above. The acidlevels in such suitable ionomers may be neutralized to controlresiliency, impact resistance and other like properties. In addition,other fillers with ionomer carriers may be used to modify (e.g.preferably increase) the specific gravity of the thermoplastic blend tocontrol the moment of inertia and other like properties. Exemplarycommercially available thermoplastic materials suitable for use in aboundary layer 14 of a golf ball 10 of the present invention include,for example, the following materials and/or blends of the followingmaterials: HYTRELeand/or HYLENE®products from DuPont, Wilmington, Del.,PEBAX® products from Elf Atochem, Philadelphia, Pa., SURLYN® productsfrom DuPont, and/or ESCOR® or IOTEK® products from Exxon Chemical,Houston, Tex.

[0054] The Shore D hardness of the boundary layer 14 ranges from 50 to75, as measured according to ASTM D-2290. It is preferred that theboundary layer 14 have a hardness of between about 55-70 Shore D. In apreferred embodiment, the boundary layer 14 has a Shore D hardness inthe range of 58-65. One reason for preferring a boundary layer 14 with aShore D hardness of 75 or lower is to improve the feel of the resultantgolf ball. It is also preferred that the boundary layer 14 is composedof a blend of SURLYN® ionomer resins.

[0055] SURLYN® 8150, 9150, and 6320 are, respectively, an ionomer resincomposed of a sodium neutralized ethylene/methacrylic acid, an ionomerresin composed of a zinc neutralized ethylene/methacrylic acid, and anionomer resin composed of a terpolymer of ethylene, methacrylic acid andn-butyl acrylate partially neutralized with magnesium, all of which areavailable from DuPont, Polymer Products, Wilmington, Del.

[0056] Exemplary golf balls of the present invention were constructedand compared to the CALLAWAY GOLF RULE 35 FIRMFEEL golf ball. Table Twoand Table Three set forth the physical properties of the exemplary groupof golf balls #1, #2 and #3. A dozen golf balls were constructed foreach group #1, #2 and #3. Each of the boundary layers 14 of theexemplary golf balls #1, #2 and #3 were composed of an ionomer blend offorty-five weight percent SURLYN 8150, forty-five weight percent SURLYN9150 and ten weight percent SURLYN 6350. The average thickness of eachof the boundary layers 14 of the exemplary golf balls #1, #2 and #3 was0.0525 inch. The Shore D hardness of the boundary layer 14 of theexemplary golf balls #1, #2 and #3 was 62 points. The Shore D hardnessprovided in Table Three below was determined according to ASTM D2240.

[0057] Each of the covers 16 of the exemplary group of golf balls #1, #2and #3 were composed of a polytetramethylene ether glycol terminatedtoluene diisocyanate prepolymer (ADRIPRENE LF930) cured with a blend ofseventy weight percent diethyl 2,4-toluenediamine (E100) and thirtyweight percent 4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline(LONZACURE). The average thickness of each of the covers 16 of theexemplary golf balls #1, #2 and #3 was 0.030 inch. The Shore D hardnessof the covers 16 of the exemplary golf balls #1, #2 and #3 was 51points. The COR at 143 feet per second of each of the exemplary golfballs #1, #2 and #3 was 79.42 points. TABLE TWO Bound. Layer CoverBound. Layer Cover Ball Shore D Shore D Thickness Thickness COR Ball(points) (points) (inch) (inch) (points) 1 62 51 0.0525 0.030 79.42 2 6251 0.0525 0.030 79.42 3 62 51 0.0525 0.030 79.42

[0058] The average weight of each of the exemplary golf balls #1, #2 and#3 was 45.29 grams. The PGA compression of each of the exemplary golfballs #1, #2 and #3 was 95. The average diameter of each of theexemplary golf balls #1, #2 and #3 was 1.683 inch. The core diameter ofeach of the cores 12 of each of the exemplary golf balls #1, #2 and #3was 1.515 inches. The PGA compression of each of the cores 12 of each ofthe exemplary golf balls #1, #2 and #3 was 70 points. TABLE THREE BallBall Average Core Core Weight Compression Diameter Diameter CompressionBall (grams) (points) (inches) (inches) (points) 1 45.29 95 1.683 1.51570 2 45.29 95 1.683 1.515 70 3 45.29 95 1.683 1.515 70

[0059] Tables Four, Five, Six, Seven, Eight and Nine compare theCALLAWAY GOLF RULE 35 FIRMFEEL golf ball to the exemplary golf balls #1,#2 and #3 of the present invention. The golf balls were measured todetermine the yellowing of the thermosetting polyurethane covers afterexposure to sunlight. The color of the cover of each of the golf ballsis determined using a HUNTER COLORIMETER model ULTRA SCAN XE andmeasuring the color on a L.a. b. scale. On the “L” scale, a measurementof 100 corresponds to complete white while a measurement of 0corresponds to complete black. On the “a” scale, a negative numbercorresponds to a green color while a positive number corresponds to ared color. On the “b” scale, a negative number corresponds to a bluecolor while a positive number corresponds to a yellow color. Thus, themore positive the b measurement, the more yellow the cover. The golfballs were measured before exposure to sunlight, after four hours ofexposure to sunlight and after twenty-four hours of exposure tosunlight/night. The average of the CALLAWAY GOLF RULE 35 FIRMFEEL golfballs after four hours of exposure to sunlight is set forth in TableFive. The average of the exemplary golf balls #1, #2 and #3 of thepresent invention after four hours of exposure to sunlight is set forthin Table Six. The average of the CALLAWAY GOLF RULE 35 FIRMFEEL golfballs after twenty-four hours of exposure to sunlight/night is set forthin Table Eight. The average of the exemplary golf balls #1, #2 and #3 ofthe present invention after twenty-four hours of exposure to sunlight isset forth in Table Nine. TABLE FOUR Before After 4 Hour ExposureExposure Difference Ball L a* b* L A* b* L a* b* Rule 93.2 −1.26 9.0775.94 7.91 38.22 −17.26 9.17 29.15 35 Firm #1 Rule 93.15 −1.24 9.1876.77 7.3 38.42 −16.38 8.54 29.24 35 Firm #2 Rule 93.03 −1.28 8.88 76.657.11 37.81 −16.38 8.39 28.93 35 Firm #3 Ex. 1 95.09 −1.5 2.04 83.09 0.2721.18 −12 1.77 19.14 Ex. 2 95.12 −1.51 2.19 85.57 −0.47 19.16 −9.55 1.0416.97 Ex. 3 95.55 −1.52 2.6 89.12 −1.44 15.78 −6.43 0.08 13.18

[0060] TABLE FIVE Average for RULE 35 Balls L a* b* DE −16.67 8.70 29.1134.65

[0061] TABLE SIX Average for Exemplary Balls of the Present Invention La* b* DE −9.33 0.96 16.43 18.92

[0062] TABLE SEVEN Before After 24 Hour Exposure Exposure DifferenceBall L a* b* L a* b* L a* b* Rule 93.2 −1.26 9.07 69.42 13.12 40.59−23.78 14.38 31.52 35 Firm #1 Rule 93.15 −1.24 9.18 69.71 12.85 40.53−23.44 14.09 31.35 35 Firm #2 Rule 93.03 −1.28 8.88 70.61 12.03 40.34−22.42 13.31 31.46 35 Firm #3 Ex. 1 95.09 −1.5 2.04 73.95 3.26 24.36−21.14 4.76 22.32 Ex. 2 95.12 −1.51 2.19 79.74 1.27 21.72 −15.38 2.7819.53 Ex. 3 95.55 −1.52 2.6 86.03 −0.46 19.67 −9.52 1.06 17.07

[0063] TABLE EIGHT Average for RULE 35 Balls L a* b* DE −23.21 13.9331.44 41.49

[0064] TABLE NINE Average for Exemplary Balls L a* b* DE −15.35 2.8719.64 25.09

[0065] As is shown in Tables Four, Five, Six, Seven, Eight and Nine, theexemplary golf balls #1, #2 and #3 of the present invention have a loweryellow measurement (“b” scale) before exposure, and a lower increase inyellowing after four hours and twenty four hours as compared to theCALLAWAY GOLF RULE 35 FIRMFEEL golf balls. For example, the #3 golf ballof the present invention had a “b” measurement of 2.6 before exposure, ameasurement of 15.78 after four hours of exposure to sunlight, and ameasurement of 19.67 after twenty-four hours of exposure. The #3CALLAWAY GOLF RULE 35 FIRMFEEL golf ball had a “b” measurement of 8.88before exposure, a measurement of 37.81 after four hours of exposure tosunlight, and a measurement of 40.34 after twenty-four hours ofexposure. The golf balls were exposed to sunlight on the rooftop of abuilding in Carlsbad, Calif. (latitude 32 46 30 north, longitude 117 2506 west) on a winter day. Thus, not only do the covers 16 of the golfballs of the present invention have less yellowing to begin with, afterexposure to sunlight the covers 16 yellow less than other coverscomposed of thermosetting polyurethane.

[0066] A second exemplary set of golf balls of the present inventionwere tested for yellowing after exposure to sunlight. These secondexemplary set of golf balls were compared to other commercial golf ballswith thermosetting polyurethane covers. Each of the boundary layers 14of the second exemplary set of golf balls were composed of an ionomerblend of forty-five weight percent SURLYN 8150, forty-five weightpercent SURLYN 9150 and ten weight percent SURLYN 6350. The averagethickness of each of the boundary layers 14 of the second exemplary setof golf balls 0.0525 inch, and the Shore D hardness of the boundarylayer 14 was 62 points. The Shore D hardness was determined according toASTM D2240.

[0067] Each of the covers 16 of the second exemplary set of golf ballswere composed of a polypropylene glycol terminated toluene diisocyanateprepolymer (ADRIPRENE LFG960) cured with a blend of seventy weightpercent diethyl 2,4-toluenediamine (E100) and thirty weight percent4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline (LONZACURE). Theaverage thickness of each of the covers 16 of the second exemplary setof golf balls was 0.030 inch and the Shore D hardness of the covers 16was 51 points. The COR at 143 feet per second of each of the secondexemplary set of golf balls was 79.42 points.

[0068] As shown in FIG. 3, the second exemplary set of golf balls werecompared to the CALLAWAY GOLF RULE 35 FIRMFEEL golf ball, the MAXFLIREVOLUTION golf ball (wound) and the TITLEIST PROFESSIONAL golf ball(wound). The paint was removed from a portion of the commercial golfballs to expose the cover material. The group A golf balls of the secondexemplary set of golf balls were post cured in a natural convection typeoven and the group B golf balls of the second exemplary set of golfballs were post cured in a Lanley type oven. The golf balls were exposedfor forty-eight hours and the color difference over time was measuredfor each of the golf balls. The second exemplary set of golf balls had alower color difference over time than all of the other golf balls.

[0069] From the foregoing it is believed that those skilled in thepertinent art will recognize the meritorious advancement of thisinvention and will readily understand that while the present inventionhas been described in association with a preferred embodiment thereof,and other embodiments illustrated in the accompanying drawings, numerouschanges, modifications and substitutions of equivalents may be madetherein without departing from the spirit and scope of this inventionwhich is intended to be unlimited by the foregoing except as may appearin the following appended claims. Therefore, the embodiments of theinvention in which an exclusive property or privilege is claimed aredefined in the following appended claims.

I claim as my invention:
 1. A golf ball comprising: a core; and a coverformed over the core, the cover composed of a thermosetting polyurethanematerial formed from reactants comprising a polyurethane prepolymer and4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline, wherein the cover hasan aerodynamic surface geometry thereon.
 2. The golf ball according toclaim 1 further comprising at least one boundary layer disposed betweenthe core and the cover.
 3. The golf ball according to claim 1 whereinthe toluene diisocyanate prepolymer is a polypropylene glycol terminatedtoluene diisocyanate prepolymer with a NCO content ranging from 3.0% to6.0%.
 4. The golf ball according to claim 2 wherein the boundary layeris composed of a blend of ionomers.
 5. The golf ball according to claim1 wherein the polyurethane prepolymer is a polytetramethylene etherglycol terminated hexamethylene diisocyanate prepolymer.
 6. A golf ballcomprising: a core comprising a polybutadiene mixture; a boundary layerformed over the core, the boundary layer comprising at least one ionomermaterial; and a cover formed over the boundary layer, the cover composedof a thermosetting polyurethane material formed from reactantscomprising a polytetramethylene ether glycol terminated hexamethylenediisocyanate prepolymer and4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline, wherein the cover hasan aerodynamic surface geometry thereon.
 7. The golf ball according toclaim 6 wherein the thermosetting polyurethane material of the cover hasa Shore D hardness ranging from 30 to 60 as measured according toASTM-D2240.
 8. The golf ball according to claim 6 wherein the cover hasa thickness ranging from 0.015 inch to 0.040 inch.
 9. A golf ballcomprising: a core; and a cover formed over the core, the cover composedof a thermosetting polyurethane material formed from reactantscomprising a polytetramethylene ether glycol terminated hexamethylenediisocyanate prepolymer and a curative composed of4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline and diethyl2,4-toluenediamine, wherein the cover has an aerodynamic surfacegeometry thereon.
 10. A golf ball comprising: a core comprising apolybutadiene mixture; a boundary layer formed over the core, theboundary layer comprising a blend of ionomer materials; and a coverformed over the core, the cover composed of a thermosetting polyurethanematerial formed from reactants comprising a polytetramethylene etherglycol terminated hexamethylene diisocyanate prepolymer and a curativecomposed of 4,4′-methylenebis-(3-chloro,2,6-diethyl)-aniline and diethyl2,4-toluenediamine, wherein the cover has an aerodynamic surfacegeometry thereon.
 11. The golf ball according to claim 10 wherein thegolf ball has a PGA compression ranging from 70 points to 100 points.12. The golf ball according to claim 10 wherein the core has a PGAcompression in the range of 55 points to 80 points.
 13. The golf ballaccording to claim 10 wherein the blend of ionomer materials of theboundary layer is composed of a sodium neutralized ethylene/methacrylicacid, a zinc neutralized ethylene/methacrylic acid and a magnesiumneutralized terpolymer of ethylene, methacrylic acid and n-butylacrylate.
 14. The golf ball according to claim 10 wherein thethermosetting polyurethane material of the cover has a Shore D hardnessranging from 30 to 60 as measured according to ASTM-D2240.
 15. The golfball according to claim 10 wherein the cover has a thickness rangingfrom 0.015 inch to 0.040 inch.